-increasing your social circle(online friends don't count).

I defy this conclusion.

online friends are maybe not as socially fulfilling as face-to-face friends, but I wouldn't count them as having zero positive benefits. Especially if you have an obscure hobby/interest only shared by some - or only by a few local people. Doubly-so if you happen not to live in a big city.

I have both online and offline friends and both sets of them make up my complete social circle.

If you also happen to travel frequently - offline contact with your old circle of friends/family may be the best way to keep in touch. As a member of a family who I can truthfully say the sun-never sets upon... this is a huge benefit.